Quick-acting hold-down cam clamp



Jan. 9, 1951 v LEHMANN 2,537,594

QUICK-ACTING HOLD-DOWN CAM CLAMP- Filed June 9, 1944 i j/ I, Z I. W

Z I f (5 INVENTOR.

' Azazzrf LE/MMA A/ Patented Jan. 9, 1951 QUICK-ACTING HOLD-DOWN CAMCLAMP Albert F. Lehmann, Detroit, Mich., assignor to Special EngineeringService, Incorporated, Detroit, Mich., a corporation of MichiganApplication June 9, 1944, Serial No. 539,416 A '3 Claims.

This invention relates toa clamp.

Ina machine shop various types of clamps are used for holding work to asupporting surface while machining operations are being performed on thework or other finishing or checking operations are being performed. Insome cases a small operation on a large number of pieces of the sameshape and size requires that the piece be temporarily clamped in placethen removed and another one inserted. There might'be slight variationsin the size of these pieces but on the whole they probably would havemuch the same clamping dimensions.

The present invention has as its object a provision of a clamp for thesepieces of work which will hold them securely in spite of smallvariations of dimensions and which may be readily opened and closed sothat the work pieces may be replaced rapidly. A further object is toprovide a clamp which has a positive action without the necessity of anysprings. A further object is to provide a clamp in whichthe pressure isaccumulative and gradually increasing. This distinguishes the clamp fromthe usual toggle type of clamp wherein the pressure reaches a peak at acertain point and then reduces.

In the drawings:

Fig. 1 illustrates a view of the clamp in clamping position.

Fig. 2 shows the clamp in released position.

Fig. 3 is a sectional view on line 33 of Fig. 2.

Fig. 4 is a side elevation on line ei of Fig. 1.

A work table or base plate B is shown in the drawings with a piece ofwork W resting thereon. The clamp consists of an inverted T-shapedmember having a horizontal portion l and a vertically extending portionll. At the point !2 on member II is pivoted an operating arm orstraddling member I3 having sides which come down on either side of themember ll. Within this member 13 is a small block 14 the purpose ofwhich will appear later. At point 20 on member H the width of the memberis reduced as at 2! and an arm 22 has a bifurcated portion with sides 23which are pivoted at this point 2!]. This arm 22 has a holding portionH, a cam portion C, and a release portion R. l

The cam portion C is shaped as shown in Fig. 1 and Fig. 2 to cooperatewith the curved portion Ma. of piece l4. When the arm is in clampingposition the piece It rides up on the cam portion C and holds the arm inplace. On the holding portion H of the arm is a threaded stem 30 whichis adjustable and arranged to contact the work. The release portion ofthe arm has a point .the recessR, of arm 22.

This member M on its downthe operating arm l3 will strike heel 3! andkick arm 22 about point 25 to the position shown in Fig. 2 at which timethe member I4 is received in In this position the clamping arm 22 is ina gravitationally stable position where the back of the bifurcatedportion 23 contacts the edge of the reduced portion 2| of the member I!to serve as a stop. Figures 2 and 3.

When clamping movement is again desired the handle I3 willbe movedupwardly in the direction of the arrow of Fig. 2 at which time the blockIt will contact surface 32 leading to the cam surface C and cause thearm to fall toward the work. As it reaches the work the block M willmove over the cam surface to a clamping point.

For any desired piece of work the operator can adjust a member 39' to acertain position relative to H. After that work pieces of substantiallythe same dimensions may be quickly inserted and removed from the clamp.The operator need only strike th member 3 a sharp blow to release with afollow-up movement to throw the parts into the position of Fig. 2. Aquick upward movement will again cause the clamping after'the workpieces have been exchanged.

Due to the shape and positioning of the cam and cam block, thepositioning of the pivots l2 and 29 and the arrangement of the actuatingand clamping members, it will be seen that a positive clamping action ofrelatively great force is obtained with an extremely simple and shortmovement of the actuating lever I 3.

It will be understood that in referring in the specification and claimsto the vertical or horizontal positions of the various elements of theclamp that these horizontal and/or vertical positions are relative tothe base B, it being obvious that the base 13 can assume many differentpositions without changing the operating features of the clamp itself.

What I claim is:

1. A clamp comprising a base having an operating arm and a clamping armpivoted thereto at spaced points, a cam surface on said clamping arm onone side of its pivot point and a heel on said clamping arm on the otherside of its pivot point, means on the operating arm contacting with thecam on the clamping arm to cause clamping in one position and kickingthe heel and the clamping arm to release in another position, and athird contact surface on said clamping arm intermediate said cam surfaceand said heel to cooperate with said means to cause said clamping arm tomove to clamping position, said arms being freely movable with respectto each other except at said contact points.

2. In a quick action production clamp comprising a base member, anoperating arm and a clamping arm mounted on said base for movement onparallel spaced axes, a cam surface on.

said clamping arm on the Work side of its mounting axis and a heel onsaid clamping arm on the other side of its mounting axis, means on saidoperating arm operable to contact the cam surface of the clamping arm toexert clamping force on said arm in clamping position, said means beingpositioned to contact said heel to kick the heel and the clamping arm torelease position, and an intermediate surface between said heel and camsurface on the work side of the clamping arm axes positioned to becontacted to knock said clamping arm into work clamping position as saidoperating arm is moved to a clamping position, said arms being freelymovable with respect to each other except at said heel and surfacecontact points.

3. A clamp comprising a base having an operation arm and a clamping armpivoted thereto at spaced pionts, a cam surface on said clamping ,arm onone side of its pivot point and a heel on said clamping arm composed ofan extension of the arm beyond the base on the other side of its pivotpoint, the clamping arm being pivoted adjacent a vertical wall of thebase, the bottom of said heel extension being positioned to contact saidwall to serve as a stop for the clamping arm and provide agravitationally stable release position with said clamping arm extendingsubstantially vertically above said base, means on said operating armoperable to contact the cam surface of the clamping arm to exertclamping force on said arm in clamping position, said means beingpositioned to contact the top of said heel to kick the heel and theclamping arm to release position, and an intermediate surface adjoiningsaid cam surface positioned to be contacted to knock said clamping arminto work clamping position as said operating arm is moved to a clampingposition, said arms being freely movable with respect to each otherexcept at said heel and surface contact points.

ALBERT F. LEI-IMANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 591,421 Palmer et al Oct. 12,1897 834,402 Peick Oct. 30, 1906 2,236,439 McKenna Mar. 25, 1941 FOREIGNPATENTS Number Country Date 433,446 Great Britain Aug. 14, 1935

